#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int main(void)
{
	int money = 20;
	int soda = 1;
	int bottle = 0;
	int drink = 0;
	for (; money > 0; money--)
	{
		bottle++;
		drink++;
	}
	for (; bottle > 0; bottle -= 2)
	{
		drink++;
	}
	printf("%d", drink);
	return 0;
}